One method for providing controlled release of a drug is to provide a coating surrounding a core containing the drug. Some or all of the components of the core, including the drug, are released through one or more openings or drug delivery ports formed in the coating. Such controlled release dosage forms typically utilize osmotic pressure, diffusion or surface hydration to deliver the core's drug contents through the delivery ports.
One such controlled-release dosage form is a coated tablet having a core of two layers. One layer of the core contains drug and is in communication with an opening through the coating. The other layer is a sweller layer containing a swelling agent. The bi-layer core is surrounded by a semipermeable coating. When introduced to an environment of use, water permeates through the coating to cause the swelling agent to expand, which in turn causes the drug-containing layer to be extruded through the opening into the environment of use.
It is well known to form an opening through a pharmaceutical coating using a laser. Examples of such systems are disclosed in U.S. Pat. Nos. 5,698,119, 5,658,474 and 5,399,828. The '828 patent describes a laser drilling system for use in forming an opening through the coating of a bi-layer tablet. The two layers are of different colors. The system uses a side detector to determine which side of the tablet contains the drug, then directs one of two lasers to drill through the coating on that side. Although this system is capable of accurately determining the correct side of the tablet to drill, it has no means of verifying that the tablet has in fact been drilled to the specified opening and that the opening is completely through the coating. If the opening is incomplete, of the wrong size, or otherwise different than that specified, the release rate of the drug may be altered.
The use of a laser to form the opening through a tablet coating causes portions of the coating and potentially the drug core to be vaporized or otherwise expelled from the tablet. It is desirable to remove this debris to limit buildup of debris within the system, to minimize interference with the laser, and to reduce exposure of operators to the debris. In addition, it is desired to accomplish these functions at relatively high rates of speed for purposes of automation.
What is therefore needed is a pharmaceutical laser drilling system that is not only automated and capable of drilling the correct side of a tablet, but that is also capable of accurately determining the completeness and correctness of drilling, that removes debris generated during the drilling process, and that is capable of processing tablets at a high rate of speed.